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switch支持String
try-with-resources
catch多个异常
实例创建类型推断
数字字面量下划线分割
二进制字面量
增强的文">
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                <h2 id="新特性列表"><a href="#新特性列表" class="headerlink" title="新特性列表"></a>新特性列表</h2><p>以下是Java7中的引入的部分新特性。关于Java7更详细的介绍可参考<a href="http://www.oracle.com/technetwork/java/javase/jdk7-relnotes-418459.html" target="_blank" rel="noopener">这里</a>。</p>
<ul>
<li>switch支持String</li>
<li>try-with-resources</li>
<li>catch多个异常</li>
<li>实例创建类型推断</li>
<li>数字字面量下划线分割</li>
<li>二进制字面量</li>
<li>增强的文件系统</li>
<li>Fork/Join框架</li>
<li>其它<ul>
<li>JDBC4.1规范</li>
<li>支持动态类型语言</li>
<li>JSR341-Expression Language Specification</li>
<li>JSR203-More New I/O APIs for the Java Platform</li>
<li>桌面客户端增强</li>
</ul>
</li>
</ul>
<h2 id="一、switch支持String"><a href="#一、switch支持String" class="headerlink" title="一、switch支持String"></a>一、switch支持String</h2><p><code>switch</code>现在可以接受<code>String</code>类型的参数。示例代码如下：</p>
<pre class=" language-java"><code class="language-java">String s <span class="token operator">=</span> <span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">.</span>
<span class="token keyword">switch</span><span class="token punctuation">(</span>s<span class="token punctuation">)</span> <span class="token punctuation">{</span>
<span class="token keyword">case</span> <span class="token string">"quux"</span><span class="token operator">:</span>
    <span class="token function">processQuux</span><span class="token punctuation">(</span>s<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token comment" spellcheck="true">// fall-through</span>
<span class="token keyword">case</span> <span class="token string">"foo"</span><span class="token operator">:</span>
<span class="token keyword">case</span> <span class="token string">"bar"</span><span class="token operator">:</span>
    <span class="token function">processFooOrBar</span><span class="token punctuation">(</span>s<span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token keyword">break</span><span class="token punctuation">;</span>
<span class="token keyword">case</span> <span class="token string">"baz"</span><span class="token operator">:</span>
    <span class="token function">processBaz</span><span class="token punctuation">(</span>s<span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token comment" spellcheck="true">// fall-through</span>
<span class="token keyword">default</span><span class="token operator">:</span>
    <span class="token function">processDefault</span><span class="token punctuation">(</span>s<span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token keyword">break</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span></code></pre>
<h2 id="二、try-with-resources"><a href="#二、try-with-resources" class="headerlink" title="二、try-with-resources"></a>二、try-with-resources</h2><p>Java中某些资源是需要手动关闭的，如<code>InputStream</code>，<code>Writer</code>，<code>Sockets</code>，<code>Connection</code>等。这个新的语言特性允许try语句本身申请更多的资源，这些资源作用于try代码块，并自动关闭。</p>
<p>Java7之前的写法：</p>
<pre class=" language-java"><code class="language-java">BufferedReader br <span class="token operator">=</span> null<span class="token punctuation">;</span>
<span class="token keyword">try</span> <span class="token punctuation">{</span>
    br <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">BufferedReader</span><span class="token punctuation">(</span><span class="token keyword">new</span> <span class="token class-name">FileReader</span><span class="token punctuation">(</span>path<span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token keyword">return</span> br<span class="token punctuation">.</span><span class="token function">readLine</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span> <span class="token keyword">catch</span> <span class="token punctuation">(</span><span class="token class-name">Exception</span> e<span class="token punctuation">)</span> <span class="token punctuation">{</span>
    log<span class="token punctuation">.</span><span class="token function">error</span><span class="token punctuation">(</span><span class="token string">"BufferedReader Exception"</span><span class="token punctuation">,</span> e<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span> <span class="token keyword">finally</span> <span class="token punctuation">{</span>
    <span class="token keyword">if</span> <span class="token punctuation">(</span>br <span class="token operator">!=</span> null<span class="token punctuation">)</span> <span class="token punctuation">{</span>
        <span class="token keyword">try</span> <span class="token punctuation">{</span>
            br<span class="token punctuation">.</span><span class="token function">close</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
        <span class="token punctuation">}</span> <span class="token keyword">catch</span> <span class="token punctuation">(</span><span class="token class-name">Exception</span> e<span class="token punctuation">)</span> <span class="token punctuation">{</span>
            log<span class="token punctuation">.</span><span class="token function">error</span><span class="token punctuation">(</span><span class="token string">"BufferedReader close Exception"</span><span class="token punctuation">,</span> e<span class="token punctuation">)</span><span class="token punctuation">;</span>
        <span class="token punctuation">}</span>
    <span class="token punctuation">}</span>
<span class="token punctuation">}</span></code></pre>
<p>Java7及之后的写法：</p>
<pre class=" language-java"><code class="language-java"><span class="token keyword">try</span> <span class="token punctuation">(</span>BufferedReader br <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">BufferedReader</span><span class="token punctuation">(</span><span class="token keyword">new</span> <span class="token class-name">FileReader</span><span class="token punctuation">(</span>path<span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token keyword">return</span> br<span class="token punctuation">.</span><span class="token function">readLine</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span> <span class="token keyword">catch</span> <span class="token punctuation">(</span><span class="token class-name">Exception</span> e<span class="token punctuation">)</span> <span class="token punctuation">{</span>
    log<span class="token punctuation">.</span><span class="token function">error</span><span class="token punctuation">(</span><span class="token string">"BufferedReader Exception"</span><span class="token punctuation">,</span> e<span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span></code></pre>
<h2 id="三、catch多个异常"><a href="#三、catch多个异常" class="headerlink" title="三、catch多个异常"></a>三、catch多个异常</h2><p>自Java7开始，<code>catch</code>中可以一次性捕捉多个异常做统一处理。示例如下：</p>
<p>Java7之前的写法：</p>
<pre class=" language-java"><code class="language-java"><span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">handle</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    ExceptionThrower thrower <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">ExceptionThrower</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token keyword">try</span> <span class="token punctuation">{</span>
        thrower<span class="token punctuation">.</span><span class="token function">manyExceptions</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token punctuation">}</span> <span class="token keyword">catch</span> <span class="token punctuation">(</span><span class="token class-name">ExceptionA</span> a<span class="token punctuation">)</span> <span class="token punctuation">{</span>
        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>a<span class="token punctuation">.</span><span class="token function">getClass</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token punctuation">}</span> <span class="token keyword">catch</span> <span class="token punctuation">(</span><span class="token class-name">ExceptionB</span> b<span class="token punctuation">)</span> <span class="token punctuation">{</span>
        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>b<span class="token punctuation">.</span><span class="token function">getClass</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token punctuation">}</span> <span class="token keyword">catch</span> <span class="token punctuation">(</span><span class="token class-name">ExceptionC</span> c<span class="token punctuation">)</span> <span class="token punctuation">{</span>
        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>c<span class="token punctuation">.</span><span class="token function">getClass</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token punctuation">}</span>
<span class="token punctuation">}</span></code></pre>
<p>Java7及之后的写法：</p>
<pre class=" language-java"><code class="language-java"><span class="token keyword">public</span> <span class="token keyword">void</span> <span class="token function">handle</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    ExceptionThrower thrower <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">ExceptionThrower</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token keyword">try</span> <span class="token punctuation">{</span>
        thrower<span class="token punctuation">.</span><span class="token function">manyExceptions</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token punctuation">}</span> <span class="token keyword">catch</span> <span class="token punctuation">(</span><span class="token class-name">ExceptionA</span> <span class="token operator">|</span> ExceptionB ab<span class="token punctuation">)</span> <span class="token punctuation">{</span>
        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>ab<span class="token punctuation">.</span><span class="token function">getClass</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token punctuation">}</span> <span class="token keyword">catch</span> <span class="token punctuation">(</span><span class="token class-name">ExceptionC</span> c<span class="token punctuation">)</span> <span class="token punctuation">{</span>
        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>c<span class="token punctuation">.</span><span class="token function">getClass</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token punctuation">}</span>
<span class="token punctuation">}</span></code></pre>
<h2 id="四、实例创建类型推断"><a href="#四、实例创建类型推断" class="headerlink" title="四、实例创建类型推断"></a>四、实例创建类型推断</h2><p>从Java7开始，泛型类的实例化也不用繁琐的将泛型声明再写一遍。示例如下：</p>
<p>Java7之前的写法：</p>
<pre class=" language-java"><code class="language-java">Map<span class="token operator">&lt;</span>String<span class="token punctuation">,</span> List<span class="token operator">&lt;</span>String<span class="token operator">>></span> map <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">HashMap</span><span class="token operator">&lt;</span>String<span class="token punctuation">,</span> List<span class="token operator">&lt;</span>String<span class="token operator">>></span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
<p>Java7及之后的写法：</p>
<pre class=" language-java"><code class="language-java">Map<span class="token operator">&lt;</span>String<span class="token punctuation">,</span> List<span class="token operator">&lt;</span>String<span class="token operator">>></span> map <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">HashMap</span><span class="token operator">&lt;</span><span class="token operator">></span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
<h2 id="五、数字字面量下划线分割"><a href="#五、数字字面量下划线分割" class="headerlink" title="五、数字字面量下划线分割"></a>五、数字字面量下划线分割</h2><p>很长的数字可读性不好，在Java 7中可以使用下划线分隔长<code>int</code>以及<code>long</code>型整数了。如：</p>
<pre class=" language-java"><code class="language-java"><span class="token keyword">long</span> creditCardNumber <span class="token operator">=</span> 1234_5678_9012_3456L<span class="token punctuation">;</span>
<span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">final</span> <span class="token keyword">int</span> ONE_MILLION <span class="token operator">=</span> 1_000_000<span class="token punctuation">;</span>
<span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">final</span> <span class="token keyword">float</span> PI <span class="token operator">=</span> <span class="token number">3</span><span class="token punctuation">.</span>14_15F<span class="token punctuation">;</span></code></pre>
<h2 id="六、二进制字面量"><a href="#六、二进制字面量" class="headerlink" title="六、二进制字面量"></a>六、二进制字面量</h2><p>现在可以使用0b前缀创建二进制字面量：</p>
<pre class=" language-java"><code class="language-java"><span class="token keyword">int</span> binary <span class="token operator">=</span> 0b1001_1001<span class="token punctuation">;</span></code></pre>
<p>使用二进制字面量这种表示方式，使用非常简短的代码就可将二进制字符转换为数据类型，如在<code>byte</code>或<code>short</code>。</p>
<pre class=" language-java"><code class="language-java"><span class="token keyword">byte</span> aByte <span class="token operator">=</span> <span class="token punctuation">(</span><span class="token keyword">byte</span><span class="token punctuation">)</span> <span class="token number">0b001</span><span class="token punctuation">;</span>
<span class="token keyword">short</span> aShort <span class="token operator">=</span> <span class="token punctuation">(</span><span class="token keyword">short</span><span class="token punctuation">)</span> <span class="token number">0b010</span><span class="token punctuation">;</span></code></pre>
<h2 id="七、增强的文件系统"><a href="#七、增强的文件系统" class="headerlink" title="七、增强的文件系统"></a>七、增强的文件系统</h2><p>Java7 推出了全新的<code>NIO2.0 API</code>以此改变针对文件管理的不便，使得在<code>java.nio.file</code>包下使用<code>Path</code>、<code>Paths</code>、<code>Files</code>、<code>WatchService</code>、<code>FileSystem</code>等常用类型可以很好的简化开发人员对文件管理的编码工作。</p>
<h3 id="1-Path接口和Paths类"><a href="#1-Path接口和Paths类" class="headerlink" title="1. Path接口和Paths类"></a>1. Path接口和Paths类</h3><p><code>Path</code>接口的某些功能其实可以和<code>java.io</code>包下的<code>File</code>类等价，当然这些功能仅限于只读操作。在实际开发过程中，开发人员可以联用<code>Path</code>接口和<code>Paths</code>类，从而获取文件的一系列上下文信息。</p>
<ul>
<li><code>int getNameCount()</code>: 获取当前文件节点数</li>
<li><code>Path getFileName()</code>: 获取当前文件名称</li>
<li><code>Path getRoot()</code>: 获取当前文件根目录</li>
<li><code>Path getParent()</code>: 获取当前文件上级关联目录</li>
</ul>
<p>联用<code>Path</code>接口和<code>Paths</code>类型获取文件信息：</p>
<pre class=" language-java"><code class="language-java">Path path <span class="token operator">=</span> Paths<span class="token punctuation">.</span><span class="token function">get</span><span class="token punctuation">(</span><span class="token string">"G:/test/test.xml"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"文件节点数:"</span> <span class="token operator">+</span> path<span class="token punctuation">.</span><span class="token function">getNameCount</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"文件名称:"</span> <span class="token operator">+</span> path<span class="token punctuation">.</span><span class="token function">getFileName</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"文件根目录:"</span> <span class="token operator">+</span> path<span class="token punctuation">.</span><span class="token function">getRoot</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"文件上级关联目录:"</span> <span class="token operator">+</span> path<span class="token punctuation">.</span><span class="token function">getParent</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
<h3 id="2-Files类"><a href="#2-Files类" class="headerlink" title="2. Files类"></a>2. Files类</h3><p>联用<code>Path</code>接口和<code>Paths</code>类可以很方便的访问到目标文件的上下文信息。当然这些操作全都是只读的，如果开发人员想对文件进行其它非只读操作，比如文件的创建、修改、删除等操作，则可以使用<code>Files</code>类型进行操作。</p>
<p>Files类型常用方法如下：</p>
<ul>
<li><code>Path createFile()</code>: 在指定的目标目录创建新文件</li>
<li><code>void delete()</code>: 删除指定目标路径的文件或文件夹</li>
<li><code>Path copy()</code>: 将指定目标路径的文件拷贝到另一个文件中</li>
<li><code>Path move()</code>: 将指定目标路径的文件转移到其他路径下，并删除源文件</li>
</ul>
<p>使用<code>Files</code>类型复制、粘贴文件示例：</p>
<pre class=" language-java"><code class="language-java">Files<span class="token punctuation">.</span><span class="token function">copy</span><span class="token punctuation">(</span>Paths<span class="token punctuation">.</span><span class="token function">get</span><span class="token punctuation">(</span><span class="token string">"/test/src.xml"</span><span class="token punctuation">)</span><span class="token punctuation">,</span> Paths<span class="token punctuation">.</span><span class="token function">get</span><span class="token punctuation">(</span><span class="token string">"/test/target.xml"</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span></code></pre>
<p>使用<code>Files</code>类型来管理文件，相对于传统的I/O方式来说更加方便和简单。因为具体的操作实现将全部移交给<code>NIO2.0 API</code>，开发人员则无需关注。</p>
<h3 id="3-WatchService"><a href="#3-WatchService" class="headerlink" title="3. WatchService"></a>3. WatchService</h3><p>Java7 还为开发人员提供了一套全新的文件系统功能，那就是文件监测。在此或许有很多朋友并不知晓文件监测有何意义及目，那么请大家回想下调试成热发布功能后的Web容器。当项目迭代后并重新部署时，开发人员无需对其进行手动重启，因为Web容器一旦监测到文件发生改变后，便会自动去适应这些“变化”并重新进行内部装载。Web容器的热发布功能同样也是基于文件监测功能，所以不得不承认，文件监测功能的出现对于Java文件系统来说是具有重大意义的。</p>
<p>文件监测是基于事件驱动的，事件触发是作为监测的先决条件。开发人员可以使用<code>java.nio.file</code>包下的<code>StandardWatchEventKinds</code>类型提供的3种字面常量来定义监测事件类型，值得注意的是监测事件需要和<code>WatchService</code>实例一起进行注册。</p>
<p><code>StandardWatchEventKinds</code>类型提供的监测事件：</p>
<ul>
<li><code>ENTRY_CREATE</code>：文件或文件夹新建事件；</li>
<li><code>ENTRY_DELETE</code>：文件或文件夹删除事件；</li>
<li><code>ENTRY_MODIFY</code>：文件或文件夹粘贴事件；</li>
</ul>
<p>使用<code>WatchService</code>类实现文件监控完整示例：</p>
<pre class=" language-java"><code class="language-java"><span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">void</span> <span class="token function">testWatch</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token comment" spellcheck="true">/* 监控目标路径 */</span>
    Path path <span class="token operator">=</span> Paths<span class="token punctuation">.</span><span class="token function">get</span><span class="token punctuation">(</span><span class="token string">"G:/"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token keyword">try</span> <span class="token punctuation">{</span>
        <span class="token comment" spellcheck="true">/* 创建文件监控对象. */</span>
        WatchService watchService <span class="token operator">=</span> FileSystems<span class="token punctuation">.</span><span class="token function">getDefault</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">newWatchService</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>

        <span class="token comment" spellcheck="true">/* 注册文件监控的所有事件类型. */</span>
        path<span class="token punctuation">.</span><span class="token function">register</span><span class="token punctuation">(</span>watchService<span class="token punctuation">,</span> StandardWatchEventKinds<span class="token punctuation">.</span>ENTRY_CREATE<span class="token punctuation">,</span> StandardWatchEventKinds<span class="token punctuation">.</span>ENTRY_DELETE<span class="token punctuation">,</span>
                StandardWatchEventKinds<span class="token punctuation">.</span>ENTRY_MODIFY<span class="token punctuation">)</span><span class="token punctuation">;</span>

        <span class="token comment" spellcheck="true">/* 循环监测文件. */</span>
        <span class="token keyword">while</span> <span class="token punctuation">(</span><span class="token boolean">true</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
            WatchKey watchKey <span class="token operator">=</span> watchService<span class="token punctuation">.</span><span class="token function">take</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>

            <span class="token comment" spellcheck="true">/* 迭代触发事件的所有文件 */</span>
            <span class="token keyword">for</span> <span class="token punctuation">(</span>WatchEvent<span class="token operator">&lt;</span><span class="token operator">?</span><span class="token operator">></span> event <span class="token operator">:</span> watchKey<span class="token punctuation">.</span><span class="token function">pollEvents</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
                System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span>event<span class="token punctuation">.</span><span class="token function">context</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">.</span><span class="token function">toString</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">+</span> <span class="token string">" 事件类型："</span> <span class="token operator">+</span> event<span class="token punctuation">.</span><span class="token function">kind</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
            <span class="token punctuation">}</span>

            <span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token operator">!</span>watchKey<span class="token punctuation">.</span><span class="token function">reset</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
                <span class="token keyword">return</span><span class="token punctuation">;</span>
            <span class="token punctuation">}</span>
        <span class="token punctuation">}</span>
    <span class="token punctuation">}</span> <span class="token keyword">catch</span> <span class="token punctuation">(</span><span class="token class-name">Exception</span> e<span class="token punctuation">)</span> <span class="token punctuation">{</span>
        e<span class="token punctuation">.</span><span class="token function">printStackTrace</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token punctuation">}</span>
<span class="token punctuation">}</span></code></pre>
<p>通过上述程序示例我们可以看出，使用<code>WatchService</code>接口进行文件监控非常简单和方便。首先我们需要定义好目标监控路径，然后调用<code>FileSystems</code>类型的<code>newWatchService()</code>方法创建<code>WatchService</code>对象。接下来我们还需使用<code>Path</code>接口的<code>register()</code>方法注册<code>WatchService</code>实例及监控事件。当这些基础作业层全部准备好后，我们再编写外围实时监测循环。最后迭代<code>WatchKey</code>来获取所有触发监控事件的文件即可。</p>
<h2 id="八、Fork-Join框架"><a href="#八、Fork-Join框架" class="headerlink" title="八、Fork/Join框架"></a>八、Fork/Join框架</h2><h3 id="1-什么是Fork-Join框架"><a href="#1-什么是Fork-Join框架" class="headerlink" title="1. 什么是Fork/Join框架"></a>1. 什么是Fork/Join框架</h3><p>Java7提供的一个用于并行执行任务的框架，是一个把大任务分割成若干个小任务，最终汇总每个小任务结果后得到大任务结果的框架。</p>
<p>Fork/Join的运行流程图如下：</p>
<p><img src="https://res.infoq.com/articles/fork-join-introduction/zh/resources/21.png" alt="Fork/Join的运行流程图"></p>
<h3 id="2-工作窃取算法"><a href="#2-工作窃取算法" class="headerlink" title="2. 工作窃取算法"></a>2. 工作窃取算法</h3><p>工作窃取（work-stealing）算法是指某个线程从其他队列里窃取任务来执行。工作窃取的运行流程图如下：</p>
<p><img src="https://res.infoq.com/articles/fork-join-introduction/zh/resources/image3.png" alt="工作窃取的运行流程图"></p>
<p>工作窃取算法的优点是充分利用线程进行并行计算，并减少了线程间的竞争，其缺点是在某些情况下还是存在竞争，比如双端队列里只有一个任务时。并且消耗了更多的系统资源，比如创建多个线程和多个双端队列。</p>
<h3 id="3-Fork-Join框架的介绍"><a href="#3-Fork-Join框架的介绍" class="headerlink" title="3. Fork/Join框架的介绍"></a>3. Fork/Join框架的介绍</h3><p>设计一个Fork/Join框架，主要有以下两步骤：</p>
<p>第一步分割任务。首先我们需要有一个fork类来把大任务分割成子任务，有可能子任务还是很大，所以还需要不停的分割，直到分割出的子任务足够小。</p>
<p>第二步执行任务并合并结果。分割的子任务分别放在双端队列里，然后几个启动线程分别从双端队列里获取任务执行。子任务执行完的结果都统一放在一个队列里，启动一个线程从队列里拿数据，然后合并这些数据。</p>
<p>Fork/Join使用两个类来完成以上两件事情：</p>
<p>ForkJoinTask：我们要使用ForkJoin框架，必须首先创建一个ForkJoin任务。它提供在任务中执行fork()和join()操作的机制，通常情况下我们不需要直接继承ForkJoinTask类，而只需要继承它的子类，Fork/Join框架提供了以下两个子类：<br>RecursiveAction：用于没有返回结果的任务。<br>RecursiveTask ：用于有返回结果的任务。<br>ForkJoinPool ：ForkJoinTask需要通过ForkJoinPool来执行，任务分割出的子任务会添加到当前工作线程所维护的双端队列中，进入队列的头部。当一个工作线程的队列里暂时没有任务时，它会随机从其他工作线程的队列的尾部获取一个任务。</p>
<h3 id="4-Fork-Join框架使用示例"><a href="#4-Fork-Join框架使用示例" class="headerlink" title="4. Fork/Join框架使用示例"></a>4. Fork/Join框架使用示例</h3><p>让我们通过一个简单的需求来使用下<code>Fork／Join</code>框架，需求是：计算<code>1 + 2 + 3 + 4</code>的结果。</p>
<p>使用<code>Fork/Join</code>框架首先要考虑到的是如何分割任务，如果我们希望每个子任务最多执行两个数的相加，那么我们设置分割的阈值是<code>2</code>，由于是<code>4</code>个数字相加，所以<code>Fork/Join</code>框架会把这个任务<code>fork</code>成两个子任务，子任务一负责计算<code>1 + 2</code>，子任务二负责计算<code>3 + 4</code>，然后再<code>join</code>两个子任务的结果。</p>
<p>因为是有结果的任务，所以必须继承<code>RecursiveTask</code>，实现代码如下：</p>
<pre class=" language-java"><code class="language-java"><span class="token keyword">package</span> com<span class="token punctuation">.</span>blinkfox<span class="token punctuation">.</span>test<span class="token punctuation">.</span>other<span class="token punctuation">;</span>

<span class="token keyword">import</span> java<span class="token punctuation">.</span>util<span class="token punctuation">.</span>concurrent<span class="token punctuation">.</span>ExecutionException<span class="token punctuation">;</span>
<span class="token keyword">import</span> java<span class="token punctuation">.</span>util<span class="token punctuation">.</span>concurrent<span class="token punctuation">.</span>ForkJoinPool<span class="token punctuation">;</span>
<span class="token keyword">import</span> java<span class="token punctuation">.</span>util<span class="token punctuation">.</span>concurrent<span class="token punctuation">.</span>Future<span class="token punctuation">;</span>
<span class="token keyword">import</span> java<span class="token punctuation">.</span>util<span class="token punctuation">.</span>concurrent<span class="token punctuation">.</span>RecursiveTask<span class="token punctuation">;</span>

<span class="token comment" spellcheck="true">/**
 * CountTask.
 *
 * @author blinkfox on 2018-01-03.
 */</span>
<span class="token keyword">public</span> <span class="token keyword">class</span> <span class="token class-name">CountTask</span> <span class="token keyword">extends</span> <span class="token class-name">RecursiveTask</span><span class="token operator">&lt;</span>Integer<span class="token operator">></span> <span class="token punctuation">{</span>

    <span class="token comment" spellcheck="true">/** 阈值. */</span>
    <span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">final</span> <span class="token keyword">int</span> THRESHOLD <span class="token operator">=</span> <span class="token number">2</span><span class="token punctuation">;</span>

    <span class="token comment" spellcheck="true">/** 计算的开始值. */</span>
    <span class="token keyword">private</span> <span class="token keyword">int</span> start<span class="token punctuation">;</span>

    <span class="token comment" spellcheck="true">/** 计算的结束值. */</span>
    <span class="token keyword">private</span> <span class="token keyword">int</span> end<span class="token punctuation">;</span>

    <span class="token comment" spellcheck="true">/**
     * 构造方法.
     *
     * @param start 计算的开始值
     * @param end 计算的结束值
     */</span>
    <span class="token keyword">public</span> <span class="token function">CountTask</span><span class="token punctuation">(</span><span class="token keyword">int</span> start<span class="token punctuation">,</span> <span class="token keyword">int</span> end<span class="token punctuation">)</span> <span class="token punctuation">{</span>
        <span class="token keyword">this</span><span class="token punctuation">.</span>start <span class="token operator">=</span> start<span class="token punctuation">;</span>
        <span class="token keyword">this</span><span class="token punctuation">.</span>end <span class="token operator">=</span> end<span class="token punctuation">;</span>
    <span class="token punctuation">}</span>

    <span class="token comment" spellcheck="true">/**
     * 执行计算的方法.
     *
     * @return int型结果
     */</span>
    <span class="token annotation punctuation">@Override</span>
    <span class="token keyword">protected</span> Integer <span class="token function">compute</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
        <span class="token keyword">int</span> sum <span class="token operator">=</span> <span class="token number">0</span><span class="token punctuation">;</span>

        <span class="token comment" spellcheck="true">// 如果任务足够小就计算任务.</span>
        <span class="token keyword">if</span> <span class="token punctuation">(</span><span class="token punctuation">(</span>end <span class="token operator">-</span> start<span class="token punctuation">)</span> <span class="token operator">&lt;=</span> THRESHOLD<span class="token punctuation">)</span> <span class="token punctuation">{</span>
            <span class="token keyword">for</span> <span class="token punctuation">(</span><span class="token keyword">int</span> i <span class="token operator">=</span> start<span class="token punctuation">;</span> i <span class="token operator">&lt;=</span> end<span class="token punctuation">;</span> i<span class="token operator">++</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
                sum <span class="token operator">+=</span> i<span class="token punctuation">;</span>
            <span class="token punctuation">}</span>
        <span class="token punctuation">}</span> <span class="token keyword">else</span> <span class="token punctuation">{</span>
            <span class="token comment" spellcheck="true">// 如果任务大于阈值，就分裂成两个子任务来计算.</span>
            <span class="token keyword">int</span> middle <span class="token operator">=</span> <span class="token punctuation">(</span>start <span class="token operator">+</span> end<span class="token punctuation">)</span> <span class="token operator">/</span> <span class="token number">2</span><span class="token punctuation">;</span>
            CountTask leftTask <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">CountTask</span><span class="token punctuation">(</span>start<span class="token punctuation">,</span> middle<span class="token punctuation">)</span><span class="token punctuation">;</span>
            CountTask rightTask <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">CountTask</span><span class="token punctuation">(</span>middle <span class="token operator">+</span> <span class="token number">1</span><span class="token punctuation">,</span> end<span class="token punctuation">)</span><span class="token punctuation">;</span>

            <span class="token comment" spellcheck="true">// 等待子任务执行完，并得到结果，再合并执行结果.</span>
            leftTask<span class="token punctuation">.</span><span class="token function">fork</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
            rightTask<span class="token punctuation">.</span><span class="token function">fork</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
            sum <span class="token operator">=</span> leftTask<span class="token punctuation">.</span><span class="token function">join</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token operator">+</span> rightTask<span class="token punctuation">.</span><span class="token function">join</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
        <span class="token punctuation">}</span>
        <span class="token keyword">return</span> sum<span class="token punctuation">;</span>
    <span class="token punctuation">}</span>

    <span class="token comment" spellcheck="true">/**
     * main方法.
     *
     * @param args 数组参数
     */</span>
    <span class="token keyword">public</span> <span class="token keyword">static</span> <span class="token keyword">void</span> <span class="token function">main</span><span class="token punctuation">(</span>String<span class="token punctuation">[</span><span class="token punctuation">]</span> args<span class="token punctuation">)</span> <span class="token keyword">throws</span> ExecutionException<span class="token punctuation">,</span> InterruptedException <span class="token punctuation">{</span>
        ForkJoinPool fkPool <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">ForkJoinPool</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
        CountTask task <span class="token operator">=</span> <span class="token keyword">new</span> <span class="token class-name">CountTask</span><span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">4</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
        Future<span class="token operator">&lt;</span>Integer<span class="token operator">></span> result <span class="token operator">=</span> fkPool<span class="token punctuation">.</span><span class="token function">submit</span><span class="token punctuation">(</span>task<span class="token punctuation">)</span><span class="token punctuation">;</span>
        System<span class="token punctuation">.</span>out<span class="token punctuation">.</span><span class="token function">println</span><span class="token punctuation">(</span><span class="token string">"result:"</span> <span class="token operator">+</span> result<span class="token punctuation">.</span><span class="token function">get</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token punctuation">}</span>

<span class="token punctuation">}</span></code></pre>
<h2 id="九、其它"><a href="#九、其它" class="headerlink" title="九、其它"></a>九、其它</h2><h3 id="1-JDBC4-1规范"><a href="#1-JDBC4-1规范" class="headerlink" title="1. JDBC4.1规范"></a>1. JDBC4.1规范</h3><p>JDBC4.1主要更新了两个新特性，分别是：</p>
<h4 id="1-Connection，ResultSet-和-Statement-都实现了Closeable-接口"><a href="#1-Connection，ResultSet-和-Statement-都实现了Closeable-接口" class="headerlink" title="(1). Connection，ResultSet 和 Statement 都实现了Closeable 接口"></a>(1). Connection，ResultSet 和 Statement 都实现了Closeable 接口</h4><p><code>Connection</code>，<code>ResultSet</code>和<code>Statement</code>都实现了<code>Closeable</code>接口，所有在<code>try-with-resources</code>语句中调用，就可以自动关闭相关资源了。</p>
<h4 id="2-RowSet-1-1"><a href="#2-RowSet-1-1" class="headerlink" title="(2). RowSet 1.1"></a>(2). RowSet 1.1</h4><p>引入<code>RowSetFactory</code>接口和<code>RowSetProvider</code>类，可以创建JDBC driver支持的各种`Rowsets。</p>
<pre class=" language-java"><code class="language-java">RowSetFactory myRowSetFactory <span class="token operator">=</span> null<span class="token punctuation">;</span>
JdbcRowSet jdbcRs <span class="token operator">=</span> null<span class="token punctuation">;</span>
ResultSet rs <span class="token operator">=</span> null<span class="token punctuation">;</span>
Statement stmt <span class="token operator">=</span> null<span class="token punctuation">;</span>

<span class="token keyword">try</span> <span class="token punctuation">{</span>
  myRowSetFactory <span class="token operator">=</span> RowSetProvider<span class="token punctuation">.</span><span class="token function">newFactory</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span><span class="token comment" spellcheck="true">//用缺省的RowSetFactory 实现</span>
  jdbcRs <span class="token operator">=</span> myRowSetFactory<span class="token punctuation">.</span><span class="token function">createJdbcRowSet</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>

  <span class="token comment" spellcheck="true">//创建一个 JdbcRowSet 对象，配置数据库连接属性</span>
  jdbcRs<span class="token punctuation">.</span><span class="token function">setUrl</span><span class="token punctuation">(</span><span class="token string">"jdbc:myDriver:myAttribute"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
  jdbcRs<span class="token punctuation">.</span><span class="token function">setUsername</span><span class="token punctuation">(</span>username<span class="token punctuation">)</span><span class="token punctuation">;</span>
  jdbcRs<span class="token punctuation">.</span><span class="token function">setPassword</span><span class="token punctuation">(</span>password<span class="token punctuation">)</span><span class="token punctuation">;</span>

  jdbcRs<span class="token punctuation">.</span><span class="token function">setCommand</span><span class="token punctuation">(</span><span class="token string">"select ID from TEST"</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
  jdbcRs<span class="token punctuation">.</span><span class="token function">execute</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span></code></pre>
<p><code>RowSetFactory</code>接口包括了创建不同类型的RowSet的方法：</p>
<ul>
<li>createCachedRowSet</li>
<li>createFilteredRowSet</li>
<li>createJdbcRowSet</li>
<li>createJoinRowSet</li>
<li>createWebRowSet</li>
</ul>
<h3 id="2-略"><a href="#2-略" class="headerlink" title="2. 略"></a>2. 略</h3><hr>
<p>参考文档：</p>
<ul>
<li><a href="http://www.oracle.com/technetwork/java/javase/jdk7-relnotes-418459.html" target="_blank" rel="noopener">JavaSE7 Features and Enhancements</a></li>
<li><a href="https://segmentfault.com/a/1190000004417830" target="_blank" rel="noopener">Java7的新特性</a></li>
<li><a href="http://www.infoq.com/cn/articles/fork-join-introduction" target="_blank" rel="noopener">Fork/Join框架介绍</a></li>
</ul>

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